It is important within the food industry to avoid as far as possible that the often very aggressive medium is allowed to accumulate in seal pockets, slots or the like. Furthermore it is an advantage if the parts which might come in contact with the medium are easy to clean. Possible accumulations of the sealed medium often very rapidly form colonies of bacteria within the food industry, which of course is unacceptable.
Thus, from the medium side there shall be no slits, cavities or other spaces into which the medium can penetrate and accumulate in dirt pockets, which may be difficult to clean.
Current seals normally used for lead-through shafts are not designed from the viewpoint of avoiding that the sealed medium in any way accumulate in the sealing arrangement. Instead they have recesses, slots or the like, in which any sealing element is placed. However, these recesses, slots or the like at the same time constitute dirt pockets for the sealed medium, which is unacceptable within e.g. the food industry.